Tropones and Tropolones

In contrast to benzene rings, tropones, 18, and tropolones, 19, are easily hydrogenated over palladium catalysts at low temperatures and pressures in neutral solvents (Eqns. 17.21-22). 2,83 acetic acid the ketone group of the saturated tropolone is also reduced.  

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Another seven-membered ring that shows some aromatic character is tropone (44). This molecule would have an aromatic sextet if the two C=0 electrons stayed away from the ring and resided near the electronegative oxygen atom. In fact, tropones are stable compounds, and tropolones (45) are found in nature. However, analyses of dipole moments, NMR spectra, and X-ray diffraction measurements show that tropones and tropolones display appreciable bond alternations. ... 

A. General Syntheses of Heterocyclic Fused Tropones and Tropolones. 86... 

B. Syntheses of Tropones and Tropolones Fused to Individual Heterocyclic... 

Examples of different types of tropones and tropolones fused to a five-membered heterocyclic ring are given in Scheme 1. Different fusion with respect to the heteroatom or group (Z) leads to... 

According to Nozoe [56FOR( 13)232], the term tropoids includes the three types mentioned above troponoids is a common name for tropones and tropolones. 

Heterocyclic Fused Tropones and Tropolones from Carbonyl and Heterocyclic Dicarbonyl Compounds (Scheme 8)... 

For reviews of tropones and tropolones. see Pietra Acc Chem. Res. 1979,12. 132-138 Nozoc Pure Appl. Chem. 1971, 28. 239-280. 

Many fused tropones show typical absorptions of tropone itself (73CRV293, p. 329). Considerable differences are often observed in the longwave region of tropones and tropolones (e.g., 65BCJ301). UV data of typical heterocyclic troponoids are listed in Tables XIV-XVI (cf. Scheme 76). 

IR Bands of Tropones and Tropolones with Fused Heterocyclic Rings... 

The dipole moments of some fused tropones and tropolones are listed in Table XVIII. 

Reaction with tropone and tropolone.5 The reagent reacts with tropone to give the highly reactive ketone (1) the following mechanism is proposed ... 

See Table IX, Footnote (a). b IO = isooctane, CH = cyclohexane. cd Parent tropone and tropolone, respectively. Benzo[d]tropone (numbered like type 304). Quaternary salt (2,3-dimethyl-8-oxocycloheptoxazolium perchlorate, 507 63UP2) Amax(log e) 243 (4.28) and 333 (3.93), region A 492 (2.62), region B. 

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